Computerized documents (hereinafter referred to as electronic documents) are frequently used today. Electronic documents are very convenient because they can be readily sent from one party to another party by way of E-mail attachments. On the other hand, new kinds of problems such as leakage of information are occurred while distribution of electronic documents is easy.
Today, a technique for restricting operations such as display, edit, and print operations have been introduced for some types of files such as PDF (Portable Document Format) files. Only authorized users are allowed to perform operations, such as printing, of such files.
In image forming apparatuses, print job data sent from a host computer through a network is bitmapped to generate image data for printing. The image data is temporarily stored in a hard disk drive of the image forming apparatus. However, the data may be held in the hard disk drive after completion of printing. The purpose of this is to read the image data of any of the originals stored in the hard disk drive to print it again. The image data can be sent to another apparatus. The function of storing a frequently used electronic documents in a document box provided in a hard disk drive in this way is called the document box function. A document box is like a folder or directory in a file system.
Image data of confidential documents may be stored in a document box. Therefore, it is desirable that only predetermined users are allowed to access document boxes. According to Japanese Patent Laid-Open No. 11-227267, a password is set for a document box so as to allow only the users who know the password to access image data in the document box.
As described above, even image data of an electronic document on which operations are restricted on a host computer may be held in an image forming apparatus after printing operation is performed. Predetermined operations on the image data thus generated for printing cannot be restricted in the same way they are restricted on the original electronic document. In some cases, operations on an electronic document are restricted but operations on data in an image format specific to an image forming apparatus are not restricted. Both of them can be generated by scanning an original document and stored in the image forming apparatus. In such cases, operation restrictions equivalent to those applied on the electronic document cannot be applied on the data in the image format specific to the image forming apparatus.
If image data is stored in a document box described in Japanese Patent Laid-Open No. 11-227267, access to the image data can be restricted through use of a password. However, once the image data is transferred as an email attachment from the image forming apparatus to another apparatus, the image data can no longer be protected. That is, the technique described in Japanese Patent Laid-Open No. 11-227267 cannot appropriately protect image data once it is retrieved from a document box.